#include <iostream>
using namespace std;
 


#define PI 3.14159
int test1()
{
    // 编译后变成：cout << "Value of PI :" << 3.14159 << endl; 
    cout << "Value of PI :" << PI << endl; 
 
    return 0;
}

#define DEBUG
void test2(){
    // 条件编译
#ifdef DEBUG
   cerr <<"debug run" << endl;
#endif

#ifdef RELEASE
   cerr <<"release run" << endl; // 不编译
#endif
}

void test3(){
    // 预定义宏
    cout << "Value of __LINE__ : " << __LINE__ << endl; // 29
    cout << "Value of __FILE__ : " << __FILE__ << endl; // D:\Coding\vscodeProjects\TestCpp\Define\test.cpp
    cout << "Value of __DATE__ : " << __DATE__ << endl; // Apr  9 2022
    cout << "Value of __TIME__ : " << __TIME__ << endl; // 16:04:12
}

int main(){
    test3();
}